Process for producing phosphorus

ABSTRACT

A process for producing phosphorus, which comprises supplying a phosphorite ore to melting simultaneously with feeding paraffin or higher fatty acids C 20  -C 24 , melting the phosphorite ore in the presence of a reducing agent and quartzite with the formation of flue gases containing vapours of phosphorus. The flue gases are subjected to cleaning and condensation with the recovery of phosphorus and the formation of a slime. The slime is subjected to extraction with paraffin or higher fatty acids C 16  -C 24  to recover phosphorus therefrom.

FIELD OF THE INVENTION

The present invention relates to the production of phosphorus andcompounds thereof and, more specifically, to a process for producingphosphorus, which is useful in the production of phosphoric acid andcommercial phosphates.

BACKGROUND OF THE INVENTION

Known in the art is a process for producing phosphorus from flue gasescontaining vapours of phosphorus, carbon monoxide, gaseous compounds offluorine and silicon, fine dust, by treating thereof at a temperature offrom 130° to 350° C. with steam supplied in an amount of 10 to 100 g perm³ of the gas, followed by condensation of the gases with water torecover phosphorus and produce a slime. The slime into which therepasses up to 12% of phosphorus, as calculated for the mass of phosphorusproduced, is delivered to further processing (SU, A, No. 1017670.)

This prior art process is noted for a considerable slime formation, butthe recovery of phosphorus from such slimes is hindered due to thepresence of asphalt-resin stabilizers therein.

Also known is a process for producing phosphorus, comprising melting ofa phosphorite ore (phosphate rock) in the presence of a reducing agent(coke) and quartzite with the formation of flue gases containing vapoursof phosphorus, outdusting thereof in electric filters and condensationwith water to recover phosphorus and a slime. The latter is delivered toreprocessing to obtain phosphorus (SU, A, No. 981211). The flue gasesprior to the condensation are treated with vapours or an emulsion of anorganosilicon liquid such as polymethylsiloxane.

In carrying out this process 10% of phosphorus by mass of the producedphosphorus passes into the slime which has an increased content ofasphalt-resin substances.

Furthermore, the employed organosilicon liquids are hardly available andhazardous, so that commercial implementation of the process becomesrather difficult.

From the slimes obtained in the above-described processes it isdifficult to recover phosphorus due to a considerable stabilization ofphosphorus particles therein by asphalt-resin substances. They areusually subjected to an extraction with organic agents such as carbontetrachloride in the presence of various oxidizing agents (SU, A, No.856976). The degree of recovery of phosphorus from such slimes is notmore than 70%. Furthermore, the extraction is carried out at a massratio of the extraction agent to the slime of 8-10:1, so that theprocess in general is complicated. Hydrolysis of the extraction agentresults in the formation of hydrochloric acid which has a detrimentaleffect on the corrosion-resistance of the equipment.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a process forproducing phosphorus, which would enable a maximum yield of commercialphosphorus.

This object is accomplished by the provision of a process for producingphosphorus, comprising melting a phosphorite ore in the presence of areducing agent and quartzite with the formation of flue gases containingvapours of phosphorus, purification thereof and condensation with waterto recover phosphorus and to obtain a slime, followed by recovery ofphosphorus from the latter by means of an organic extraction agent,wherein, according to the present invention, in the supply of thephosphorite ore to melting, paraffin or higher fatty acids C₂₀ -C₂₄is/are also supplied and as the organic extraction agent for therecovery of phosphorus from the slime use is made of paraffin or higherfatty acids C₁₆ -C₂₄.

The reagents introduced into the process perform a dual function. Firstof all, they contribute to minimization of the slime-formation andprovide conditions for the formation of stabilized slimes due todecomposition of asphalt-resin substances in the gas phase. The use ofsuch reagents makes it possible to increase the yield of phosphorus fromthe gas phase into a commercial product up to 94-99% and lower thepassage of phosphorus into the slime down to 5% based on the mass of thephosphorus produced. They also act as extraction agents and, when usedin the treatment of slightly-stabilized slimes, ensure a maximum yieldof commercial phosphorus (up to 99.6%). To create favourable conditionsfor condensation of the flue gases and minimize the slime formation, itis advisable to carry out the supply of the paraffin in an amount of0.05 to 0.2% by mass of the supplied phosphorite ore, while the higherfatty acids C₂₀ -C₂₄ should be supplied in an amount of from 0.05 to0.3% by mass of the supplied phosphorite ore.

To ensure a maximum recovery of phosphorus from the resulting slime, itis preferable to extract it with paraffin at a mass ratio of from 1:1 to1:4 or with higher fatty acids C₁₆ -C₂₄ at a mass ratio of 1:1 to 1:2.

DETAILED DESCRIPTION OF THE INVENTION

The process according to the present invention is carried out in thefollowing manner.

A charge containing a phosphorite ore, a reducing agent (coke) andquartzite is fed into a continuous-action furnace wherein it is meltedat the temperature of 1,500° C. At the same time, molten paraffin issupplied into the furnace through nozzles at a rate of 0.05-0.2% by massof the phosphorite ore, or molten fatty acids C₂₀ -C₂₄ at a rate of 0.05to 0.3% by mass of the phosphorite ore, which reagents are deposited onthe charge surface. The supply of paraffin or higher fatty acids can bealso effected in a mixture with the charge.

As the charge moves to the melting zone, it is heated by the flow of theresulting flue gases, ascending from this zone and containing vapours ofphosphorus, carbon monoxide, gaseous compounds of fluorine and silicon,and fine dust. In the furnace zone with a temperature of 350° to 500° C.paraffin or the higher fatty acids are evaporated from the surface ofthe charge and pass, together with the flue gases, onto electric filtersvia a gas duct.

The charge, while moving to the zone located at the bottom part of thefurnace, is melted at the temperature of 1,500° C. This results in theformation of flue gases containing vapours of phosphorus, carbonmonoxide, fluorine and silicon compounds, fine dust, as well as slag andferrophosphorus. The flow of the resulting gases moves countercurrentlyto the charge movement.

As the temperature of the flue gases becomes lower than the dew point(300° C.) of the paraffin vapours or of the vapours of higher fattyacids C₂₀ -C₂₄, the latter ensure blocking of the active centres of finedust, so that its coagulation occurs. This dust contains asphalt-resinsubstances contributing to the highest degree of stabilization of theslimes formed later on. These substances are decomposed by the paraffinor the above-mentioned higher fatty acids before reaching the stage ofcondensation. At the same time, the paraffin or higher fatty acids donot react with phosphorus, since at these temperatures it is in the gasstate.

Owing to such an effect of paraffin or higher fatty acids C₂₀ -C₂₄ thecoagulated dust is substantially fully captured by the electric filter.After the filter the cleaned flue gases are fed to condensation effectedby way of spraying them with water. On the bottom of the condensationbath a layer of relatively pure commercial phosphorus is accumulated inan amount of more than 94% of its mass in the gas phase. Over this layerthere is a mixture referred to as a slime, consisting of droplets orglobules of phosphorus, solid impurities, and water. According to theprocess of this invention, up to 5% of the entire mass of the phosphorusproduced apasses into this slime, this being 2-4 times lesser than inthe prior art processes. Along with the reduction of the amount of theslime, it also has a low degree of stabilization due to the presence oflow-molecular hydrocarbons therein. The low-molecular hydrocarbons arewell-extracted by paraffin or fatty acids C₁₆ -C₂₄. For this reason theywere suggested for use as an extraction agent for the recovery ofphosphorus from the slime produced in the process of the presentinvention. It is desirable to extract the slime with paraffin at a massratio of 1:1 to 1:4, or with higher fatty acids at a mass ratio of 1:1to 1:2. This will enable a yield of commercial phosphorus in theextraction as high as up to 99.6%.

EXAMPLE 1

Into a continuous-action furnace 29.0 t of a charge consisting of 20 tof a phosphorite ore, 4 t of quartzite, and 5.0 t of coke are loaded,Simultaneously through nozzles a molten paraffin is sprayed into thefurnace at the rate of 0.05% by mass of the phosphorite ore which isdeposited on the surface of the charge. As the latter moves to themelting zone it is heated by a flow of ascending flue gases formedearlier. At the temperature of 350° C. evaporation of paraffin occurs.The resulting vapours are mixed with the flue gases and delivered topurification and condensation. The charge, while passing into the zonelocated in the bottom section of the furnace, gets molten at thetemperature of 1,500° C. This results in the formation of flue gasscontaining vapours of phosphorus, carbon monoxide, fluorine and siliconcompounds, fine dust, as well as slag and ferrophosphorus. The flow ofthe resulting flue gases is directed countercurrently to the chargemovement.

The flue gases in a mixture with the paraffin vapours are cleaned in anelectric filter, and then they are delivered to condensation. At thebottom part of the condensation bath 1.9 t of commercial phosphorus areaccumulated. The upper layer comprises a slime into which 0.1 t ofphosphorus passes. The yield of commercial phosphorus amounts to 95% ofits mass in the gas phase. The mass of the formed slime is 0.2 t. 0.2 tof the slime is extracted with 0.4 t of molten paraffin, i.e. at themass ratio of 1:2, at the temperature of 70° C.

The yield of the commercial phosphorus from the slime is 99.4% by mass.

EXAMPLE 2

Into a continuous-action furnace 29.0 t of a charge consisting of 20 tof a phosphorite ore, 4 t of quartzite and 5.0 t of coke are loaded.Simultaneously molten paraffin is sprayed into the furnace throughnozzles at the ratio of 0.2% by mass of the phosphorite ore, whichparaffin settles on the surface of the charge. As the charge moves tothe melting zone, it is heated by a flow of ascending flue gases formedearlier. The paraffin evaporates at the temperature of 300° C. Theresulting vapours are mixed with the flue gases and delivered tocleaning and condensation. The charge, while passing into the zone ofthe bottom part of the furnace, melts at the temperature of 1,500° C.This results in the formation of flue gases containing vapours ofphosphorus, carbon monoxide, compounds of fluorine and silicon, finedust, as well as slag and ferrophosphorus. The flow of the resultingflue gases moves countercurrently to the charge movement.

The cleaning of the flue gases mixed with the paraffin vapours iseffected in an electric filter, whereafter they are subjected tocondensation. In the lower part of the condensation bath 1.99 t ofphosphorus are accumulated. The yield of commercial phosphorus is 99.5%of its mass in the gas phase. The upper layer comprises a slime intowhich 0.01 t of phosphorus passes. The mass of the obtained slime is0.02 t. 0.02 t of the slime is subjected to extraction with 0.02 t ofmolten paraffin, i.e. at the mass ratio of 1:1, at the temperature of60° C.

The yield of commercial phosphorus from the slime is 95.5% by mass.

EXAMPLE 3

Into a continuous-action furnace 29.0 t of a charge consisting of 20 tof a phosphorite ore, 4 t of quartzite, and 5.0 t of coke are loaded.Simultaneously molten higher fatty acids C₂₀ -C₂₄ are sprayed into thefurnace through nozzles at the rate of 0.3% by mass of the phosphoriteore, which acids settle on the surface of the charge. As the chargemoves towards the melting zone, it is heated by a flow of ascending fluegases formed earlier. At the temperature of 400° C. the fatty acids areevaporated. The resulting vapours are mixed with the flue gases and fedto cleaning and condensation. The charge, while passing into the zonelocated at the bottom of the furnace is melted at the temperature of1,500° C. Flue gases are thus formed, which contain vapours ofphosphorus, carbon monoxide, compounds of fluorine and silicon, finedust, as well as slag and ferrophosphorus. The flow of the resultingflue gases moves countercurrently to the charge movement.

Cleaning of the flue gases mixed with the vapours of higher fatty acidsis effected in an electric filter, followed by their condensation. 1.98t of commercial phosphorus are accumulated at the bottom section of thecondensation bath.

The yield of commercial phosphorus is 99% of its mass in the gas phase.The upper layer comprises a slime whereinto 0.2 t of phosphorus passes.The slime mass is 0.04 t. 0.04 t of the slime is subjected to extractionwith 0.04 t of molten higher fatty acids C₁₆ -C₂₄, i.e. at their massratio of 1:1, at the temperature of 70° C.

The yield of commercial phosphorus from the slime is 95.0% by mass.

EXAMPLE 4

Into a continuous-action furnace 29.0 t of a charge consisting of 20 tof a phosphorite ore, 4 t of quartzite, and 5.0 t of coke are charged.Simultaneously molten higher fatty acids C₂₀ -C₂₄ are sprayed into thefurnace through nozzles at the rate of 0.5% by mass of the phosphoriteore, which acids settle on the surface of the charge. As the chargemoves towards the melting zone, it is heated by a flow of ascending fluegases formed earlier. The fatty acids evaporate at the temperature of500° C. The resulting vapours are mixed with the flue gases anddelivered to cleaning and condensation. The charge, while passing intothe zone located in the bottom part of the furnace, is melted at thetemperature of 1,500° C. This results in the formation of flue gasescontaining vapours of phosphorus, carbon monoxide, fluorine and siliconcompounds, fine dust, as well as slag and ferrophosphorus. The flow ofthe resulting flue gases moves countercurrently to the charge movement.

The cleaning of the flue gases in a mixture with vapours of the higherfatty acids is effected in an electric filter, whereafter they aresubjected to condensation. In the bottom section of the condensationbath 1.88 t of commercial phosphorus are accumulated. The yield ofcommercial phosphorus is 94% of its mass in the gas phase.

The upper layer comprises a slime, whereinto 0.12 t of phosphorus pass.The mass of the resulting slime is 0.24 t. 0.24 t of the slime issubjected to extraction with 0.48 t of molten higher fatty acids C₁₆-C₂₄, i.e. at their mass ratio of 1:2, at the temperature of 60° C.

The yield of commercial phosphorus from the slime is 99.6% by mass.

EXAMPLE 5

Into a continuous-action furnace 29.0 t of a charge consisting of 20 tof a phosphorite ore, 4 t of quartzite and 5.0 t of coke are loaded.Simultaneously molten paraffin is sprayed into the furnace throughnozzles at the rate of 0.1% by mass of the phosphorite ore, whichparaffin settles on the surface of the charge. As the charge gets movingtowards the melting zone it is heated with a flow of flue gases formedearlier. As the temperature of 350° C. the paraffin evaporates. Theresulting vapours are mixed with the flue gases and delivered tocleaning and condensation. The charge passing into the zone located inthe bottom section of the furnace melts at the temperature of 1,500° C.This results in the formation of flue gases containing vapours ofphosphorus, a mixture of carbon, fluorine, and silicon compounds, finedust, as well as slag and ferrophosphorus. The flow of the formed fluegases moves countercurrently to the charge movement.

The cleaning of the flue gases mixed with the paraffin vapours iseffected in an electric filter, whereafter they are subjected tocondensation. In the lower section of the condensation bath 1.94 t ofcommercial phosphorus are accumulated. The yield of the phosphorusproduced is 97% of its mass in the gas phase. The upper layer comprisesa slime, whereinto 0.06 t of phosphorus passes. The mass of theresulting slime is 0.12 t. 0.12 t of the slime is subjected toextraction with 0.24 t of molten higher fatty acids C₁₆ -C₂₄, i.e. atthe mass ratio thereof of 1:2, at the temperature of 60° C.

The yield of commercial phosphorus from the slime is equal to 99.6% bymass.

What is claimed is:
 1. A process for producing phosphoruscomprising:supplying a phosphorite ore to melting simultaneously withfeeding molten paraffin or molten higher fatty acids C₂₀ -C₂₄ ; meltingof the phosphorite ore in the presence of a reducing agent and quartzitewith the formation of flue gases containing vapours of phosphorus;cleaning of the flue gases and condensation thereof with water torecover phosphorus with the formation of a slime; recovering phosphorusfrom the slime by treatment thereof with an organic extraction agentselected from the group consisting of molten paraffin and molten higherfatty acids C₁₆ -C₂₄.
 2. A process as claimed in claim 1, wherein thesupply of molten paraffin is effected in an amount of 0.05 to 0.2% bymass of the supplied phosphorite ore.
 3. A process as claimed in claim1, wherein the supply of molten higher fatty acids C₂₀ -C₂₄ is effectedin an amount of 0.05 to 0.3% by mass of the supplied phosphorite ore. 4.A process as claimed in claim 1, wherein for the recovery of phosphorusthe slime is subjected to extraction with molten paraffin at a massratio thereof of 1:1-4.
 5. A process as claimed in claim 1, wherein forthe recovery of phosphorus the slime is extracted with molten higherfatty acids C₁₆ -C₂₄ at a mass ratio thereof of 1:1-2.